Nozzle for spraying liquid fuel

ABSTRACT

A nozzle for atomization of liquid fuel by air flowing through the nozzle ( 20 ), with an air entry area ( 50 ), an air exit area ( 52 ) and a flow path ( 54 ) which connects the air entry area ( 50 ) to the air exit area ( 52 ), the nozzle ( 20 ) being made of ceramic material, an air guidance device ( 56 ) being provided in the air entry area ( 50 ) which imparts a swirl to the inflowing air, and the air guidance device ( 56 ) being an integral part of the nozzle ( 20 ). Furthermore, there is a heater ( 10 ) equipped with such a nozzle ( 20 ) for mobile applications.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a nozzle for atomization of liquid fuel bymeans of the air flowing through the nozzle, with an air entry area, anair exit area and a flow path which connects the air entry area to theair exit area.

2. Description of Related Art

Generic nozzles are used, for example, in vehicle heaters. These vehicleheaters can be used, for example, as auxiliary heaters and/or stationaryheaters.

The nozzle is used to supply combustion air, due to the flow ofcombustion air the liquid fuel, for example, diesel or gasoline, beingentrained from a fuel nozzle and atomized. In this way, a mixture ofcombustion air and fuel is obtained which can be burned, optionally,after mixing with air supplied on other flow paths, by which the heatnecessary for heating operation is produced. This heat generated by aburner then heats a heat transfer medium, for example, water or air.

Nozzles of the prior art often are made of metal, e.g. as cast parts orturned parts. The disadvantage in these components is the comparativelyhigh production cost and the generally high thermal conductivity of themetals. The thermal conductivity can pose problems when the temperaturein the area of the fuel nozzle rises unduly as a result of the heatproduced in the burner. To solve the problems which are associated withmetallic nozzles, it has been proposed that a ceramic nozzle be used.

The flow behavior of the combustion air is important for the mixing ofthe combustion air with the fuel on the common path. In order to improvethe flow behavior of the combustion air, it was already proposed in DE100 39 152 A1 and corresponding U.S. Patent Application Publication2003/0022123 A1 that a swirl be imparted to the combustion air. In thisway, it is possible to distinctly improve the atomization quality andthus the efficiency of the burner, since the combustion air speed isincreased as a result of the pronounced tangential component of motion.In order to impart this swirl, a carrier with swirl blades is connectedupstream of the input area of the nozzle. However, the disadvantage inthis carrier with upstream swirl blades is that an additional componentis needed, for which reason the tolerances which exist for undisturbedoperation of the nozzle can sometimes be exceeded.

In heaters of the prior art it is, furthermore, problematical tomaintain narrow tolerances with respect to positioning of the glow plugwith regard to the inflowing fuel/air mixture.

SUMMARY OF THE INVENTION

The object of the invention is to make available a nozzle which can beeconomically produced, which has thermal conductivity which is lowcompared to metal, and which induces advantageous properties withrespect to the flow behavior of the combustion air, and calibrationproblems are to be avoided.

This object is achieved by the nozzle being made of ceramic material andhaving an air guidance means formed as an integral part thereof in theair entry area so as to impart a swirl to the inflowing air

The invention is based on the generic nozzle in that the nozzle is madeof ceramic material and the air entry area has air guidance means whichimpart a swirl to the inflowing air but improves thereon by the airguidance means being made as an integral part of the nozzle. In this waya nozzle is provided which can be economically produced. The ceramicmaterial can be easily worked, numerous versions with respect to shapingbeing possible. In particular, the air guidance means which delivers aswirl to the combustion air outside of the air entry area can be madeintegrally with the nozzle. As a result of using a ceramic, there is theadditional advantage that the area of the nozzle around the fuel needlewhich is located in the nozzle does not assume overly high temperatures,so that amounts of fuel which may be emerging from the nozzle cannotignite. The integral execution of the air guidance means makes itpossible to easily adhere to tolerances, since miscalibration of the airguidance means when the burner is being assembled is no longer possible.

The invention is advantageously developed in that the nozzle has meansfor holding a glow plug. The positioning of the glow plug with respectto the nozzle is an important parameter with regard to good startingbehavior of the burner. In heaters of the prior art, the glow plug wasgenerally held by the burner housing, so that, in this way, fluctuationsof the positioning with respect to the nozzle could occur. Thesetolerances can be precluded by the property of the nozzle of the presentinvention in that the nozzle itself has means for holding the glow plugso that the glow plug always has the same position with respect to thenozzle.

Furthermore, the nozzle in accordance with the invention isadvantageously developed in that the nozzle has at least in part anessentially cylindrical shape and that the air guidance means formschannels which are offset with respect to the radial directions. The airwhich is flowing in perpendicular to the axis of the nozzle is thereforenot radially supplied, but supplied with an offset. This offsetdetermines the swirl which is delivered to the combustion air, and thus,the flow behavior and ultimately also the properties and quality ofcombustion.

It is especially useful for the air guidance means to have essentiallytriangular base surfaces, the corners being rounded. In this way, thechannel offset can be easily implemented. The rounding of the corners isadvantageous for uniform flow behavior.

It can also be useful for the air guidance means to be made as blades.These blades can likewise provide offset channels so that, in this way,the combustion quality is benefited.

In another preferred embodiment of this invention, it is provided thatthe means for holding the glow plug are made as a hole which runsobliquely to the cylinder axis. The glow plug must then be simplyinserted into the hole for suitable positioning. A stop on the glow plugand/or within the hole provides for the glow plug to be guided into itsoptimum position with respect to the nozzle.

The nozzle in accordance with the invention is developed especiallyadvantageously in that an at least essentially cylindrical part of thenozzle has an essentially cylindrical shoulder with an increaseddiameter and that the means for holding the glow plug are made as a holewhich penetrates the shoulder which runs obliquely to the cylinder axis.In this way, the glow plug can be held in an area in which it influencesthe flow behavior of the inflowing fuel/air mixture as little aspossible. This can be easily managed by the cylindrical stop which has agreater diameter than the remaining nozzle body.

Likewise, it is especially advantageously provided that an at leastessentially cylindrical part of the nozzle has an essentiallycylindrical shoulder with an increased diameter and that the cylindricalshoulder has recesses for holding the mounting pins. These mounting pinscan be securely attached, for example, to the heat shield of the burner.The relative positioning of the nozzle is fixed in this way by recessesin the shoulder and the position of the mounting pins. Thus,installation is especially simple and is possible with only lowtolerances.

In an especially advantageous manner, it can be provided that the nozzleis a Venturi nozzle. The Venturi effect for atomization of the fuelemerging from the fuel needle can be advantageously combined in this waywith the swirl delivered to the combustion air. The effects support oneanother and thus lead to high-quality combustion.

The invention is based on the finding that a nozzle which can beeconomically produced provided with a shape which can be varied withinwide limits using a ceramic material. The shaping of the nozzle can becompleted such that the air guidance means which imparts a swirl to theentering combustion air can be made integrally with the nozzle.Furthermore, the ceramic has the advantage that an undesirably hightemperature can be avoided in the area of the fuel needle.

Another object consists in devising a heater for mobile applicationswhich can be economically produced.

This object is achieved by a heater for mobile applications, especiallymotor vehicles which is provided with a burner for combustion of afuel/air mixture having a nozzle in accordance with the presentinvention.

The invention is explained in greater detail below with reference to theaccompanying drawings which shows a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway schematic of a heater in which the nozzleof the present invention can be used;

FIG. 2 cross-sectional side view of one embodiment of a nozzle inaccordance with the invention;

FIG. 3 is a plan view of the air entry area of a nozzle in accordancewith the invention; and

FIG. 4 shows a nozzle in accordance with the invention mounted on aburner.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the drawings, the same reference numbersidentify the same or comparable components throughout the variousfigures.

FIG. 1 shows a heater 10 for use with the nozzle of the invention whichhas a burner 12 for combustion of a fuel/air mixture. The heatercomprises an annular channel fan 14 with a fan motor 36. Combustion air42 is taken in through the annular channel fan 14 via an air entryconnection 16 and is blown into a combustion air collecting space 18 onthe pressure side. The combustion air which is available in thecombustion air collecting space 18 is divided into primary air andsecondary air. The primary air is conveyed into the combustion chamber24 by a nozzle 20 which is made as a Venturi nozzle in this example. Thesecondary air is conveyed through secondary air holes 22 into thecombustion chamber 24. The division of the combustion air into primaryair and secondary air is useful in order to provide a rich, ignitablemixture at the outlet of the nozzle 20.

The nozzle 20 comprises a settling zone 26 and a diffusor 30 in order toproduce the Venturi effect. Within the nozzle 20, there is a fuel needle28. The fuel needle 28 is supplied with fuel 44 via a fuel line 82. Dueto the high flow velocity of the combustion air in the settling zone 26,the fuel which is emerging almost unpressurized from the fuel needle 28is pulled into filaments which then break down into droplets. The highair speeds which are necessary for good atomization can be achieved bygood pressure recovery of the diffusor 30.

Furthermore, over the course of the diffusor 30, the flow velocity ofthe fuel/air mixture is drastically reduced, by which low flowvelocities are accomplished in the area of the glow plug 62 which isindicated in FIG. 2. This supports the formation and propagation of apilot flame. After the starting process, i.e., ignition of the system bythe glow plug 62, the glow plug is turned off. It is used subsequentlywith the aid of resistance measurement for flame monitoring.

Within the fuel chamber 24, there is a baffle disk 32. The latterconstitutes a flow barrier so that the air emerging from the nozzle 20is forced to the outside. In this way, good mixing of the primary airwith the secondary air takes place; this is useful with respect to goodfinal combustion. The area between the nozzle 20 and baffle disk 32 isthus used as a mixing zone 34 and the area on the other side of thebaffle disk 32, i.e., the area which is downstream with respect to thebaffle disk 32, is used as a reaction zone 38. The mixture producedburns in the further course of the combustion pipe 40 and is routed outof the heater 10 by the parts which carry the exhaust gas. The heatgenerated heats the entering cold water 46 in heat exchange with theexhaust gas-carrying parts so that hot water 48 emerges from the heater10. For example, air can also be used as a heat transfer medium insteadof water.

FIG. 2 shows a partially cutaway side view of one embodiment of a nozzle20. This nozzle 20 can be used, for example, in a heater 10, as is shownin FIG. 1. The nozzle 20 is made of a ceramic material; this simplifiesthe production of the nozzle 20 as compared to metal nozzles. The nozzle20 has an air entry area 50 and an air exit area 52. The air entry area50 is connected to the air exit area 52 via the flow path 54. This flowpath 54 is divided in this example into a settling zone 26 and adiffuser 30.

In the air entry area, there is air guidance means formed of airguidance elements 56. These air guidance elements 56 are made integrallywith the ceramic nozzle 20. The air guidance elements 56 are alignedsuch that a swirl is imparted to the supplied air; this is explainedbelow with reference to FIG. 3. In the settling area 26, there can be afuel needle 28 (see, FIG. 4) so that a mixture of fuel and air emergesfrom the nozzle 20. This mixture can be ignited via a glow plug 62 whichcan be inserted into a hole 58 of the nozzle 20. The positioning of theglow plug 62 is thus fixed with respect to the nozzle 20, since the glowplug 62 is held by a hole 58 of the nozzle 20, i.e., especially not byany other parts. Thus, very low tolerances can be maintained withrespect to the installation position of the glow plug 62. The hole 58,advantageously, penetrates a cylindrical shoulder 64 of the nozzle 20,which shoulder has an enlarged radius; this has the advantage that theflow behavior of the nozzle 20 is influenced only slightly by the hole58 or by the glow plug 62 which is located in the hole 58.

FIG. 3 shows an overhead view of the air entry area 50 of a nozzle. Onepossible configuration of the air entry area 50 by air guidance elements56 is shown. The air guidance elements 56 form channels 60 for theinflowing air. These channels 60 are positioned with respect to theradii of the structure which is located essentially on an axis such thatthere is an offset. Air flowing in from the outside thus undergoes aswirl; this entails advantageous properties with respect to atomizationof the fuel which is emerging from the fuel needle which can be locatedin the settling area 26. Furthermore, in this representation, thearrangement of the opening 58 for holding the glow plug can berecognized. The opening 58 penetrates the essentially cylindricalshoulder 64. Furthermore, the shoulder 64 is provided with recesses 66.These recesses 66 define the installation position of the nozzle 20;this is explained below with respect to FIG. 4.

FIG. 4 shows a partially cutaway view of a device in accordance with theinvention. One end of the burner 12 facing the nozzle 20 is shown.

The burner 12 is bordered by a heat shield 78. On this heat shield 78,there are two mounting pins 68 in this sample embodiment. These mountingpins 68 can be welded to the heat shield 78 or to the burner 12. Themounting pins 68 define the positioning of the other components whichare described below. First of all, there is a seal 76 which preferablyis formed of a mica layer and a graphite layer, the mica layer facingthe burner 12 and the graphite layer facing the nozzle 20. The ceramicnozzle 20 follows and is positionally fixed on the mounting pins 68 withits recesses 66 (FIG. 3). A fuel feed 70 is connected to the fuel needle28 and is seated on the nozzle 20. This fuel feed 70 is positioned,likewise, by mounting pins 68 by means of holes 84 which are provided ina side flange. The fuel feed 70 is supplied with fuel by a fuel line 82in which there is a fuel sensor 80. The fuel feed 70 is followed by aspring 72 which is also seated on the mounting pins 68. The spring 72 isheld by clamping disks 74 which sit immovably on the mounting pins 68.The spring 72 is shown in the tensioned state in which the legs of thespring 72 are, for example, parallel to the interposed disk. In therelieved state of the spring 72, the legs of the spring 72 are bent upin the direction to the interposed disk. The glow plug, which is notshown in FIG. 4, is positioned in agreement with the embodiment ofnozzle 20 shown in FIG. 2 by this nozzle and is held by a wire spring(not shown) which is supported on the nozzle 20.

The fuel feed 70, and thus, the fuel needle 28 are automatically alignedin this way with respect to the nozzle 20. Therefore, only twocomponents are involved which influence the fuel feed and mixing of thefuel with the combustion air, so that very small tolerances can bemaintained; this is possible by axial mounting on the same mounting pins68. Likewise, the glow plug 62 can be positioned exactly with respect tothe nozzle 20 and the burner 12. The production of the structure shownin FIG. 4 can be completely automated. In particular, the mountingdirection is uniformly axial so that only “threading” of the components76, 20, 70, 72 and 74 need be performed. The seal 76 makes availableheat insulation, coupling of the nozzle ceramic 20 to the metal of theheat shield 78, and tolerance compensation. The structure can beadvantageously mounted by power-controlled pressing of the clampingdisks 74 onto the mounting pins 68 so that, with respect to the heat andtemperature properties of the structure, uniform prerequisites can becreated. Imparted by the spring force of the spring 72, tolerances dueto the varied heating of the components, different final temperatures ofthe components and different coefficients of temperature expansion canbe compensated.

The features of the invention disclosed in the description above, in thedrawings and in the claims can be important to the implementation of theinvention both individually and also in any combination.

1. Nozzle for atomization of liquid fuel by means of air flowing througha nozzle (20) with an air entry area (50), an air exit area (52) and aflow path (54) which connects the air entry area (50) to the air exitarea (52), characterized in that the nozzle (20) formed of ceramicmaterial, that, in the air entry area (50), there are air guidanceelements (56) which are adapted to impart a swirl to the inflowing air,and that the air guidance elements (56) are formed as an integral partof the nozzle (20).
 2. Nozzle as claimed in claim 1, wherein the nozzle(20) has means (58) for holding a glow plug (62).
 3. Nozzle as claimedin claim 1, wherein the nozzle (20) has, at least in part, anessentially cylindrical shape and wherein the air guidance elements (56)form channels (60) which are offset with respect to radial directions.4. Nozzle as claimed in claim 1, wherein the air guidance elements (56)have essentially triangular base surfaces and rounded corners.
 5. Nozzleas claimed in 1, wherein the air guidance elements (56) are blades. 6.Nozzle as claimed in claim 2, wherein the means for holding the glowplug (62) is a hole (58) which runs obliquely to a center axis of thenozzle.
 7. Nozzle as claimed in claim 2, wherein an at least essentiallycylindrical part of the nozzle (20) has an essentially cylindricalshoulder (64) with an increased diameter and wherein the means forholding the glow plug (62) is a hole (58) which penetrates the shoulder(64) and which runs obliquely to a center axis of the cylindrical part.8. Nozzle as claimed in 1, wherein an at least essentially cylindricalpart of the nozzle (20) has an essentially cylindrical shoulder (64)with an increased diameter and wherein the cylindrical shoulder (64) hasrecesses (66) for holding mounting pins (68).
 9. Nozzle as claimed inclaim 1, wherein the nozzle (20) is a Venturi nozzle.
 10. Heater (10)for mobile applications, especially motor vehicles, with a burner (12)for combustion of a fuel/air mixture, the burner (12) having a nozzlecomprising: an air entry area, an air exit area and a flow path whichconnects the air entry area to the air exit area, wherein the nozzle isformed of ceramic material, in the air entry area, there are airguidance elements which are adapted to impart a swirl to the inflowingair, and the air guidance elements are formed as an integral part of thenozzle.
 11. Heater as claimed in claim 10, wherein the nozzle has meansfor holding a glow plug.
 12. Heater as claimed in claim 10, wherein thenozzle has, at least in part, an essentially cylindrical shape andwherein the air guidance elements form channels which are offset withrespect to radial directions.
 13. Heater as claimed in claim 10, whereinthe air guidance elements have essentially triangular base surfaces androunded comers.
 14. Heater as claimed in claim 10, wherein the airguidance elements are blades.
 15. Heater as claimed in claim 11, whereinthe means for holding the glow plug is a hole which runs obliquely to acenter axis of the nozzle.
 16. Heater as claimed in claim 11, wherein anat least essentially cylindrical part of the nozzle has an essentiallycylindrical shoulder with an increased diameter and wherein the meansfor holding the glow plug is a hole which penetrates the shoulder andwhich runs obliquely to a center axis of the cylindrical part. 17.Heater as claimed in claim 10, wherein an at least essentiallycylindrical part of the nozzle has an essentially cylindrical shoulderwith an increased diameter and wherein the cylindrical shoulder hasrecesses holding mounting pins.
 18. Heater as claimed in claim 10,wherein the nozzle is a Venturi nozzle.